Natural Hazards Research Australia has called attention to the recent flash flooding in Texas, which resulted in significant loss of life and property.
The organisation is urging Australian stakeholders to consider the implications of such events for local communities, particularly as thousands of Australians reside in areas that could experience similar rapid-onset flooding.
Flash floods, as described by the Bureau of Meteorology (BoM), are characterised by a sudden rise in water levels within approximately six hours of intense rainfall.
These events are often unpredictable, with water levels rising quickly and sometimes without formal warning, leaving individuals to rely on their own observations.
Natural Hazards Research Australia research has documented at least 130 fatalities from flash floods in eastern Australia between 2000 and 2017. The majority of these incidents involved people attempting to cross flooded waterways.
The risk is not limited to residents; visitors, motorists, and those engaged in outdoor activities can also be affected.
Several Australian regions are identified as being at heightened risk of flash flooding, including southeast Queensland, the Hunter Valley, the New South Wales Central Coast, Sydney, Melbourne, Hobart, and Adelaide.
Notable incidents in recent years include the 2022 Eugowra floods, which led to two deaths and the rescue of approximately 150 people, and the 2011 Toowoomba and Grantham floods, which resulted in 21 fatalities.
Natural Hazards Research Australia said urban development and climate change are contributing to an increased likelihood of flash flooding.
As cities expand and impervious surfaces become more common, runoff during heavy rainfall events intensifies.
Warmer atmospheric conditions are also expected to increase the frequency of intense rain.
The BoM issues Severe Thunderstorm and Severe Weather Warnings for heavy rainfall events likely to cause flash flooding. However, the unpredictability of flash floods makes timely warnings challenging.
Natural Hazards Research Australia’s research indicated that the language used in official warnings is sometimes misunderstood, and that individuals often rely on local knowledge or informal networks when making decisions during emergencies.
Responsibility for issuing flash flood warnings in Australia is shared between state and territory governments, often in collaboration with local councils.
While some jurisdictions, such as Moreton Bay and Brisbane in Queensland and Newcastle and Parramatta in New South Wales, have developed localised warning systems, many high-risk areas do not have dedicated local alerts.
NHRA has outlined several approaches to mitigate flash flood risk. These include:
The organisation is also supporting research to improve forecasting of extreme rainfall events and to better understand community needs regarding severe weather information.
Land-use planning is another key consideration, with recommendations to avoid placing sensitive facilities, such as schools and aged care centres, in areas prone to flash flooding.
In locations where the risk to life is particularly high, assisted relocation of vulnerable structures may be warranted.
A recent report from Willis has projected that global insured losses from natural catastrophes in 2025 will again exceed $100 billion, continuing a trend seen over the past six years.
The Willis Natural Catastrophe Review attributed this to a series of major events, including the January wildfires in Los Angeles, which have become the costliest wildfire event for insurers to date, with estimated losses above $40 billion.
Other significant events this year have included wildfires in Japan and South Korea, a record tornado season in the US, Australia’s first cyclone landfall near Brisbane in five decades, and Ireland’s highest recorded wind speed.
